TORONTO — Back on Feb. 27 at Steinbrenner Field, Derek Jeter stood in front of his locker and vowed to be relevant until the imminent end of his glorious career.

“If I ever felt that I wasn’t important,” the Yankees’ captain declared, “then I would have left a long time ago.”

Well, he’s still important, all right — maybe even more important than he has been in a few years, given the paucity of production around him. And because he’s so important, it hurts the Yankees all the more when he lets them down.

That’s precisely what happened Tuesday night at Rogers Centre, when Jeter’s second homer of the season and a walk couldn’t make up for a pair of mental misfires on defense. The Yankees lost an ugly, 7-6 game to the Blue Jays, their climb out of a six-run hole having gone for naught, when rookie Yangervis Solarte’s throwing error on a Melky Cabrera bunt allowed Jose Reyes to score from second base.

“You would’ve liked to have won it,” Jeter said of the team’s fourth straight loss, which neutralizes the four-game winning streak that preceded this schneid. “It was a situation where good teams capitalize on mistakes. They did. We capitalized on mistakes, and then they came back and won the game.”

We’re not used to Jeter making many mistakes at all. If there was one part of his mythology that came closest to reality, it was the impeccability of Jeter’s baseball brain. However, we’ve seen a few senior moments during his farewell season; this time, two of them occurred on consecutive plays.

In the bottom of the fifth inning, gutsy Yankees starting pitcher David Phelps, already trailing by a 3-0 score, was on the verge of working his way out of a first-and-second, none-out jam. The right-hander struck out Cabrera and retired Adam Lind on a flyout to center field, and he induced cleanup hitter Edwin Encarnacion to chop one to Jeter in the hole.

“He’s out if he just goes to first,” manager Joe Girardi said of the play. “A lot of times they look to take the easier out, but he’s out if he goes to first.”

Jeter looked for the easier out. At second, the speedy Reyes might have beaten the throw. So Jeter looked to third, where Solarte wasn’t covering the bag. Then he threw to first, and Encarnacion beat the belated relay, loading the bases.

“Usually, when the ball’s in the hole, I go to second or third,” Jeter said. “It was the wrong decision, obviously, and he beat me to first.”

Jeter added: “I should’ve known that [Mark Teixeira] was playing more over in the hole [and not holding Reyes on first base]. Reyes had a huge lead, and I couldn’t get him at second.”

If Phelps could have retired the next batter, Colby Rasmus, then all would have been forgiven and forgotten. But Rasmus smashed a curveball off the right field wall, and Munenori Kawasaki and Reyes scored easily. As Encarnacion hit third base, Rasmus nearly had made his way to second, and Jeter took the throw from cutoff man Brian Roberts and chased Rasmus back to first. With Teixeira ready to take Jeter’s throw at first, and with Encarnacion heading home, Jeter tried to catch up to Rasmus and slap a tag on him before Encarnacion scored. However, the 27-year-old Rasmus outran Jeter, who turns 40 Thursday, and dove back into first safely. Jeter didn’t catch Encarnacion, so the Jays suddenly had a 6-0 advantage.

“[With a] guy at third base, there’s not really much time to throw back and forth,” Jeter said. “The guy’s creeping [toward home]. I made the decision to go after him, and he beat me back to the bag.”

His explanations were perfectly reasonable. It’s just that we’re not accustomed to asking him for explanations. At least not until this season.

In a 10-2 loss to Seattle on June 2, Jeter let Kyle Seager leg out a triple because he didn’t realize the ball was fair. And in a more innocuous yet buzz-worthy moment at the Yankees’ home opener, April 7 against Baltimore, Jeter jogged on a long fly ball to left field he thought would leave the field of play and then nearly got thrown out trying to get a double when the hit didn’t clear the fence.

This quite flawed Yankees roster could use miracles from its shortstop, and so far, the only shocking development has been his occasional brain hiccups. Which presents one more obstacle to a team already facing plenty of them.